Process for stabilizing polyolefines



United States Patent PROCESS FOR STABILIZING POLYOLEFINES Hugo Malz, Leverkusen, Friedrich Lob'er and Otto Bayer,

Leverkusen-Bayerwerk, and Hans Scheurlen, Leverkusen, Germany, assignors to Farbenfabriken Bayer Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Dec. 29, 1959, Ser. No. 862,460

Claims priority, application Germany Jan. 9, 1959 10 Claims. (Cl. 26045.9)

This invention relates to the stabilization of polyolefines. Polymeric olefines, such as for example polyethylene, polypropylene or polybutylene, experience uncontrollable changes under the action of atmospheric oxygen and ozone, and these changes become apparent as undesirable discolourations and as a deterioration in the mechanical properties of plastics manufactured therefrom. The influence of heat and light considerably promotes such degradation and embrittlement processes, so that polyolefines seem unsuitable for many purposes of use.

An attempt has already been made to prevent such aging phenomena in polyolefines by adding anti-oxidizing agents and stabilizers. In addition to such agents which are known as antioxidants in connection with natural and synthetic rubber (for example alkyl phenols, p-phenylene diamine and naphthylamine derivatives), there have inter alia also been proposed for these purposes sulphurcontaining compounds, such as thiuram disulphides, phenol sulphides and mercaptans. The action of such compounds is however, often only limited and usually only slight, especially when the polyolefines are under continuous stress. In addition, when the'said compounds are used, there frequently occurs a discolouration of the polymers and a considerable nuisance due to odours during the manufacture and processing of the mixturm.

It has now been found that polyolefines can be pro tected in an excellent manner against the harmful influence of atmospheric oxygen and ozone, even with the simultaneous effect of heat and light, if thiolor thionothiol-phosphoric acid ester-S-amides or -S-sulphenamides are added to the said polyolefines.

The compounds employed according to the invention can be characterized by the general formula or SO -Y, in which X and Y have the meaning pre viously indicated. Moreover, the radicals R and R together with the amide nitrogen, can be members of a ring system which can for example be a 5- or 6-membered ring, and which can containbesides the amide nitrd genother hetero atoms, such as for example nitrogen, oxygen or sulphur, and which if desired can also be substitut-ed. n is 1 or 2.

The compounds used according to the invention can for example be obtained by the processes described in US. patent specification No. 2,891,059 by reacting amine sulphene halides or N-halogen amine or amide compounds with the alkali salts of thiol or thionothiol phosphoric acid esters.

As substituents, the hydrocarbon radicals, which are advantageously those with up to 12 carbon atoms, can for example contain halogens, more especially chlorine or bromine, or amino or nitro groups.

The following Table 1 sets out a number of the stabilizers used according to the invention, without however the scope of the class of compounds claimed being restricted in any way:

TABLE 1 (l) (C I-I5O)2P-SSN(CH=l)z B.p.o.os: 118

Thiol-thionophosphoric acid-0,0-diethylester-S-dimethyl sulphenamide undistillable oil Thiolthionophosphoric acid-0,0-diethy1 ester-S-diethyl sulphenamide (C2H5O)21;'- S S I H undistillable oil Thiol-thionophosphoric acid-0,0-diethyl ester-S-sulphene piperidide C2 5 (C2H50)2PSSN undistillable Oil Thiol-thionophosphoric acid-0,0-diethyl ester-S-cyc1ohexyl- (N -ethy1 -sulphenamide Thiol-thionophosphoric acid-O,O-dietl1y1 ester-S-dicyclohexylsulphenamide Thiol-thionophosphoric acid-()i,)-diethy1 ester-S-cyclohexyl- Thiol-thionophosphoric acid-0,0-diisobutyl ester-S-dicyclo- Thiol-phosphorie acid-0,0-dimethyl ester-S-(N-methyD- carbonic acid ethyl ester amide 13.1 .04; 137to140 o. p

C-CH:

Thiol-thionophosphoric acid-0,0-diethyl ester-S-carbonic acid ethyl ester amide M.P. to 8 C.

l-CH2 (CzH5O)zfi-SN Ml. 96 C.

C-CHz I5 Thiol'thionophosphoric acid-0,0-diethylester-S-succinimide Thiol-thionophosphoric acid-0,0-diphenyl ester'S-(N-ethyD- carbonic acid ethyl ester amide Thiol-thlonophosphoric acid0,0-diethy1 ester-S-(N-methyl)- benzene sulphonic acid amide Thiol-thionophosphoric acid-0,0-diphenyl ester-S- (N-methyl)- benzene sulphonic acid amide 'Ihiol-thlonophosphoric acid-0,0-diethyl ester-S-acetanilide (1s) (C2H5O)2I E;s-1 -o11 M.P. 54 c.

Thiol-thionophosphorie acid-0,0-diethy1-S-formanilide (19) C EN (l1C3H7O)z1;-SN 011 s CaHn-tlt.

Thiol-thlonophosphoric acid-O,O-di-norm.propylester-S- (N-tert.octyl -cyanamide Thiol-thionophosphoric acid-0,0-diethylester-S-phthalimide The compounds to be used according to the invention can be added to the polyolefines in quantities of 0.01 to by weight advantageously 0.02 to 5% by weight, based on the polyolefines. In many cases, it may be desirable to use mixtures of the compounds claimed with one another or with other stabilizers. The compounds claimed develop their stabilizing action in the pure polymers and also in mixtures thereof with carbon black, aluminium powder, fillers and dyestuffs.

The stabilizers can be incorporated in the usual manner, for example by treating the polyolefines in powder form with the stabilizers in a kneader, in a ball mill or on a roller. A particularly uniform distribution of the stabilizers in the polyolefines is produced if the mixture is conveyed at a temperature above the melting point of the polyolefines through a heatable extrusion press. The polyolefine powder can also be treated with solutions of the stabilizers in a suitable solvent which can easily be re oved again.

4 Examples of the polyolefines are polyethylene, polypropylene and polybutylene.

The following examples serve for further explaining the process of the invention. The parts and percentages given are by weight if not otherwise stated.

Example 1 A polyethylene prepared by the low-pressure process and having an average molecular weight of about 90,000 was mixed on a roller mill heated to 160 C. with 0.5% of one of the compounds as set out in the following Table 2. The sheet obtained in this way was granulated and moulded in an injection moulding machine to form standard small rods having the dimensions 6 4 mm. The notch impact strength of these test elements was measured in accordance with DIN 53453 at different times during a storage period lasting up to 32 days at C. and an oxygen pressure of 21 atm. gauge.

The following Table shows the notch impact strength of the polyethylene samples stabilized with the compounds according to the invention. The values correspond to the average of 10 separate measurements in each case. For comparison purposes, a sample of polyethylene without stabilizer is also indicated and furthermore results with the compounds numbered 9 and 10 which are the best known stabilizers.

CO-OH:

1. (olH5o)2I sN 33.9 35.9 36.1

s oo-onl s. (CzH O)1IfiS-ITISO.-;NO 33.3 35.5 31.7

S OH:

9. P(O-C(;H4C9H19)3 31.8 33.9 3-9 tlert. C4Ha 10. OH-GCHa 35.7 35.7 1.8

I tert. 04H) Instead of the polyethylene there can be used also polypropylene, e.g. an isotactic polypropylene obtained from propylene with Ziegler catalysts having an atactic content of about 5% and a density of about 0.91 g./cm. These polypropylenes show similar improvements of the notched impact strength values as the polyethylene.

We claim:

1. In the process for stabilizing a member selected from the group consisting of polyethylene, polypropylene and polybutylene the improvement which comprises using as stabilizer 0.01-l0% by weight, based on the weight of said monoolefinic polymer of compounds of the general formula:

n PS,,N Rz0 R4 in which R R and R represent a member selected from the group consisting of substituted and unsubstituted hydrocarbon radicals, and wherein R represents furthermore the groups --CEN 0 [I O-X and SO Y

in which X stands for a member selected from the group consisting of hydrogen, substituted and unsubstituted hydrocarbon radicals, alkoxy radicals, aralkoxy radicals, and aroxy radicals and Y stands for substituted and unsubstituted hydrocarbon radicals, R represents a member selected from the group consisting of hydrogen, substituted and unsubstituted hydrocarbon radicals and in those cases in which R does not stand for the nitrile group, represents R the groups it -CX and AO Y, in which X and Y have the meaning indicated above, R and R represent furthermore if they are directly connected together with the amide nitrogen members (C2H50)21]T-S-S1TI H S (EH5 is used as stabilizer.

3. Process as claimed in claim 1 wherein a compound of the formula is used as stabilizer.

4. Process as claimed in claim 1 wherein a compound of the formula S CH3 is used as stabilizer.

5. Process as claimed in claim 1 wherein a compound of the formula (C2H5O)2II |-SSN(CH3)2 References Cited in the file of this patent UNITED STATES PATENTS 2,891,059 Malz et al June 16, 1959 

1. IN THE PROCESS FOR STABILIZING A MEMBER SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE, POLYPROPYLENE AND POLYBUTYLENE THE IMPROVEMENT WHICH COMPRISES USING AS STABILIZER 0.01-10% BY WEIGHT, BASED ON THE WEIGHT OF SAID MONOOLEFINIC POLYMER OF COMPOUNDS OF THE GENERAL FORMULA: 